The present disclosure relates to a power amplifier circuit. Mobile communication devices such as cellular phones typically include a power amplifier circuit having transistors. Such a power amplifier circuit is known to have a good linearity of a transmission signal by attenuating harmonic components included in an amplified transmission signal.
For instance, U.S. Patent Application Publication No. 2013/0029619 discloses a configuration in which a plurality of harmonic termination circuits for short-circuiting harmonic components such as the second-order, third-order, and fourth-order harmonic components of a transmission signal to ground are disposed on the output side of an amplifier.
One specific example of such a harmonic termination circuit is a filter circuit having a frequency characteristic that achieves low impedance at the frequency of a harmonic to be attenuated. In recent years, due to increased transmission capacities of cellular phones and the like, for example, as seen in carrier aggregation (CA) technology, the number of frequency bands to be used has been being increased. Thus, the frequency ranges of harmonics to be attenuated also become wider. In the configuration disclosed in U.S. Patent Application Publication No. 2013/0029619, the bandwidths of the harmonics to be attenuated can become insufficient.